restructuration

adlib/core/nat.lp

adlib/core/nat_ops.lp

encodings/cert_f.lp

prelude/cert_f/booleans.lp

prelude/cert_f/equalities.lp

prelude/cert_f/int.lp

prelude/cert_f/naturalnumbers.lp

prelude/cert_f/notequal.lp

prelude/core/boolean_props.lp

prelude/core/booleans.lp

prelude/core/equalities.lp

prelude/core/if_def.lp

prelude/core/notequal.lp

prelude/core/prelude.lp

prelude/core/pvs_core.lp

prelude/core/quantifier_props.lp

prelude/core/xor_def.lp

sandbox/core/rat.lp

sandbox/core/rat_explicit.lp